Charging systems for Energy Storage Devices (ESDs) often use voltage regulators, such as switching voltage regulators, pulse-width-modulation control, and linear regulators. Some charging systems can be configured to charge the ESDs (e.g., electrochemical batteries and supercapacitors) very rapidly. However, in performing this rapid charging, the ESDs, and the devices supplying the charging current can become very hot.
Even with small supercapacitors, charging systems can develop currents as. high as eight Amps and 4-5 Watts of heat may be dissipated in small supercapacitors. Excessive heat can damage the supercapacitors and cause reliability problems with the charging semiconductor device. To handle this excess heat, conventional thermal shutdown proposals would turn the charging device off until the device cooled down and then would retry the charging process. This start and stop charging process can add considerable time to the overall charging process and, in order to prevent nuisance tripping, would require the temperature at which charging stops to be set high, which could increase the risk of damage to the charging device, damage to the ESD, or even fires.
There is a need for a more efficient means for providing over-temperature protection of charging system, while still providing an efficient charging process for energy storage devices.